This invention is generally concerned with an apparatus for transporting loads in a closed installation from one position to another, and more particularly concerned with transportation of loads in a congested area filled with structural members and operating devices having very limited spatial clearances therebetween.
Arrangements for transporting loads or equipment from one position to another, during manufacturing processes, are generally known. For example, a common arrangement comprises the use of a monorail track suspended from a ceiling and supporting thereon a hoist trolley having secured thereto a suspended member such as a chain and hook adapted to be attached to a load to be moved. The hoist trolley can be moved manually or can be motorized for moving heavy objects to a desired place. Occasionally, it is desired to move the load from one track to another track which is either located parallel or at an angle to the first track. In this situation, it is necessary to have a movable portion of a track which is capable of coupling between the various tracks used in a particular system. This movable portion of the track which can be called a transfer section is generally supported on a crane which moves or rolls along one or more girders which provide a connecting access between the transfer section and the other tracks. To obtain transfer of a load from one track to another the load is moved by means of a hoist trolley from one track to the transfer section supported by the crane. Thereafter, the transfer section together with the hoist trolley and the supported load are moved by the crane to a position adjoining the other track. The other track is then coupled with the transfer section and the hoist trolley together with the load is transferred to the other track.
Another conventional form of a transfer section, commonly called a glide switch, comprises a rectangular box structure having a stationary fram supporting a sliding steel plate having secured thereto sections of straight and curved tracks. The glide switch is generally positioned in an intermediate position of a straight track adjoining the end of a second track terminating perpendicularly to the first track. If a load is to be transferred from the first to the second track, the load is moved from the first track to the switch, onto the curved track section and then moved onto the second track. As is apparent, if additional perpendicular tracks are used, each interchange between tracks requires the use of a glide switch. In view of the box structure shape of the glide switch, a substantial area is required for accommodating such a glide switch. For example, a conventional glide switch capable of supporting a heavy load will have dimensions of about 3.times.6 feet (18 sq. ft.).
Although the use of the transfer section supported by the crane or the use of a glide switch for moving loads is satisfactory in most applications, they cannot be used in areas which are congested with structural members affording very little space clearance, for example as present inside a nuclear power plant. In view of the severe spatial overhead limitations existing in the nuclear power plant, the conventional transfer section on a crane or a glide switch cannot be used.
The invention described herein uses a radial or a transfer track pivotally anchored at one end with the free end movably supported on an arcuate or support track and adapted to intercouple with free ends of a plurality of loop and/or spur tracks which extend over areas which are to be serviced by a hoist trolley. The use of an arcuate track is shown in U.S. Pat. No. 1,530,337 which describes a cupola charging machine that is supported on such arcuate track. Such known arcuate track, however, is not used in conjunction with a plurality of loop and/or spur tracks and a radial transfer track.
The load handling system, described herein, is particularly useful in transporting equipment from a point of installation to another point for inspection in an operational area which is filled with structural and operational members having limited space therebetween. The system has been designed for use in a nuclear power plant using the known Boiling Water Reactor BWR-6 and Mark III containment, such installation having a maze of pipes adjacent to a reactor core. The described load handling system permits various equipment, such as main steam isolation valves and safety relief valves, to be removed from their operative positions to an inspection area for servicing, calibration and/or replacement.
Such a nuclear power plant has a centrally located reactor core surrounded by shielding means and located in a drywell area encompassed by a drywell wall. The drywell wall is, in turn, encompassed by a containment wall. In the drywell area there is located a maze of pipes conducting water and steam and running in various horizontal and vertical directions. In addition, various equipment is located in the drywell area including a number of main steam isolation valves and safety relief valves. In view of the limited space existing between the pipes and the various equipment located in the drywell area, the presently known systems for removing the equipment from the drywell area possess certain disadvantages. For example, a load handling system using a crane requires the use of one or more girder beams for supporting the transfer section. The use of such girder beams requires sufficient space for installation. Since some of the tracks are angularly positioned with respect to the crane, the transfer section has to be provided with one or more arcuate sections of tracks so these may be aligned properly in order to effect transfer of equipment between thr transfer section and the tracks. On the other hand, a load handling system using a glide switch also requires sufficient space. Further, each track interchange requires a glide switch, additionally compounding the spatial problem. Furthermore, the load handling system has to be so constructed as to permit the various structural members of the power plant to move independently of each other in case of earth tremors. In other words, the load handling system has to be constructed so that it does not affect the seismic design of the shield wall surrounding the nuclear core.